The aims of this study are to : determine whether breast cancer as a second neoplasm in survivors of childhood cancer is related to a specific germline mutation in BRCA1 or BRCA2; determine whether potential biomarkers of cancer susceptibility are associated with an increased risk of a second malignanacy in survivors of childhood cancer; and determine whether specific patterns of familial cancers can identify those childhood cancer survivors at increased risk for second cancers. The cancers of interest include: a) those seen in the Li-Fraumeni syndrome and b) those reported to occur with increased incidence in those with germline mutations in the genes under study. We hypothesize that the incidence of germline mutations in BRCA1 and/or BRCA2 is increased in women with breast cancers that occur as a second malignancy; that germline mutations in ATM, GSTTI, and GSTM1 are associated with increased risk of SMN's; and that a positive family history of cancer is associated with increased risk of SMN's.